Patent GB-527836-A (GB)
Title: Improvements in or relating to testing electrical circuits
IPC: G06F11/16
Filed: 1939-04-04
Abstract: 527,836. Calculating-apparatus. STANDARD TELEPHONES & CABLES, Ltd. (Hatton, W., and Kozma, L.). April 4, 1939, No. 10524. [Class 106 (i)] [Also in Group XXXIX] In a system in which a number of similar pieces of apparatus are provided for the common use of a number of persons located at a distance, the electric interconnecting arrangement is such that during slack periods the pieces of apparatus are allotted for use in pairs which work in parallel so as to provide a check on their operation, but during busy periods the pieces of apparatus are allotted singly. In one embodiment, a number of calculating units are associable with a number of distant keyboards, each of which is provided with printing or other apparatus for recording the results of calculations. In a second embodiment which relates to automatic telephone systems, registercontrollers are taken into use in pairs during slack periods and control the setting up of a temporary checking connection as well as the main connection to the wanted party. Calculating apparatus, Figs. 1, 2, 3. Each unit, which has input wires A and output wires B, is provided with a finder switch LF for connection with any one of a number of keyboards OK and associated printers P. An operator wishing to use the apparatus presses a start key SK, which by means of relays FS, ST starts the finders of all the idle units. Relays T1, D1 energize in the first finder to pick up the calling potential over wiper j. If relay F is not operated, a fresh circuit is made for FS, ST, and the remaining finders continue to rotate until a second finder picks up battery potential over wiper k, when T2, D2 energize. Relay RT pulls up in both units and a signal is sent to the operator, who then sets up his problem on the keyboard OK. The calculating units receive the data by way of relays A 1-4 and send back the result digit by digit to relays B 1-4, as described in Specification 525,330. The circuits of checking relays C 1-4 are controlled by relays B 1-4 in the two units in such a way that when corresponding relays are operated no checking relay can energize. If there is a discrepancy however, at least one checking relay operates and connects up relay E in both units to prevent printing, give an alarm and stop the calculating process. Each relay RT controls a circuit for a common relay RS, which is biassed by current through a resistance OR so that it energizes when a predetermined number of units are in use, and prepares a circuit for relay F in all the finders. This relay operates under the control of D1 in the first finder to pick up a fresh call and prevents the allotment of a second unit. If a call occurs when all the units are in use, it is necessary to break a pair which are operating in parallel. In this case, relay PB1 is back due to all the relays RT being operative, and the operation of FS, ST connects up relay PB2 which causes a switch RM to hunt for a unit which is assisted by a second one. Such a unit is characterized by D1 being up and F back, and when one is found, PB3 energizes in series with F, which opens the holding circuit over wiper k of the assisting unit so that the latter is released and is enabled to receive the fresh call. Specification 525,397 also is referred to. Automatic telephone system, Fig. 4. In an exchange of the kind described in Specification 331 204, [Class 40 (iv)], in which a registercontroller associated with a finder-selector link LF, GS over a finder LKF controls the setting up of the connection by revertive impulsing, it is arranged that during slack periods, a register-controller, e.g. R1, when seized takes into use a test link TL, which in turn becomes associated with a second register-controller, e.g. R2. Dialled impulses go to both R1 and R2 and two independent connections are set up. The test link TL counts the trains of revertive impulses, and after the tens digit opens the fundamental circuit to relay the units digit until it receives a signal from R1 that the main connection is complete. For correct operation, TL should receive busy tone. If instead it receives ringing tone, it holds R1 and both trains of selectors are left standing. If the selectors are arranged for toll offering the test link TL on receiving the busy signal may cause its final selector to break in and apply a checking tone which goes over the multiple and back over the main connection and R1 to TL, R1 being held meanwhile. It may be arbitrarily fixed at what traffic level, as determined by the number of register-controllers in use, the seizure of a test link is discontinued.